nfsd: Incoming xdr_bufs may have content in tail buffer

Since the beginning, svcsock has built a received RPC Call message
by populating the xdr_buf's head, then placing the remaining
message bytes in the xdr_buf's page list. The xdr_buf's tail is
never populated.

This means that an NFSv4 COMPOUND containing an NFS WRITE operation
plus trailing operations has a page list that contains the WRITE
data payload followed by the trailing operations. NFSv4 XDR decoders
will not look in the xdr_buf's tail, ever, because svcsock never put
anything there.

To support transports that can pass the write payload in the
xdr_buf's pagelist and trailing content in the xdr_buf's tail,
introduce logic in READ_BUF that switches to the xdr_buf's tail vec
when the decoder runs out of content in rq_arg.pages.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index f8a0b6549a88..1e4edbf70052 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -615,6 +615,7 @@ struct nfsd4_compoundargs {
 	__be32 *			end;
 	struct page **			pagelist;
 	int				pagelen;
+	bool				tail;
 	__be32				tmp[8];
 	__be32 *			tmpp;
 	struct svcxdr_tmpbuf		*to_free;